I bought my Toledo built LHD 1979 258 manual in Connecticut in May 1980 with 5,000 miles on the clock. so I am pretty sure it was a genuine USA spec of the time, so I don't think the floor bracket can have been a RHD or UK modification. The bracket is welded down and is just a "U" shape with slots in the two sides for a canvas hold down strap. Beyond that I have no idea...

As an aside, I destroyed my jack a few years ago by trying to jack up something that was too heavy for it. Ever since I have been using a wind up screw jack, which doesn't fit in the bracket.... Anybody got suggestions for a good scissor jack replacement?

Also, your photo shows a nice new looking wing bracket - can you still get hold of these? I could do with one for my 304...

I'm thinking maybe later ones had the jack under the hood, but the original bracket remained beside the seat as a legacy thing. Mine was a '78 Toledo built RHD. Don't know if the under hood bracket is available new, but used ones are available on US Ebay.